Demand for broadband services is exploding. Over the past few years variety of communication devices have been connected to the internet for a variety of services. Further, with new services being offered over wireless communications the requirement of the spectrum for the services is increasing. As a result, attempts have been made to exploit the unused part of the licensed spectrum. This unused part of the spectrum is referred to as TV whitespace. Since the whitespace part of the spectrum lies in the frequency range from 50-698 MHz in US and is spread over 470-790 MHz in UK, the spectrum may be utilized for various wireless services offered to the subscribers.
Existing communication mechanisms have developed various services that employ the whitespace spectrum for communication. One of the services includes a wireless access point that operates over the whitespace spectrum. However, existing access points have their own limitations. For example, these access points do not have mechanisms to intelligently choose the available whitespace and allocate clients to the whitespaces. Further, the access points do not account for spectrum specific characteristics. This is because present allocation mechanisms assume that the spectrum is homogenous in nature and hence allocation is concentrated to one part of the spectrum. Such assumptions are good only in cases where the total range of the available spectrum is not so diverse. However, in most of the cases allocation is not concentrated to a region or band within the spectrum but it is distributed through the available spectrum. Further, these mechanisms do not take into consideration the heterogeneous nature of the spectrum and the availability of the bands through the spectrum. As a result, most of the times all the available bands in the spectrum are not exploited and the allocation becomes concentrated to only the explored part of the spectrum. Thus, whitespace selection that ignores frequency dependent propagation cannot take the benefits provided by lower frequency bands and thus resulting in inefficient spectrum allocation.
In turn, present day access points do not have efficient client location identification means as a result of which the choice of whitespaces for the clients is not done appropriately. For example, data rate of transmission per unit of the bandwidth can be higher if the clients are located close to the access points as compared to the clients who are located far from the access points. In addition, the factors such as if the client is located close to the edge of the coverage area and so on need to be considered. Whereas, these factors have not been taken into consideration in present day access points and hence there is no efficient utilization of the whitespace.
Also, existing access points assume that wireless systems possess single rate whereas the wireless systems these days are multi rate and support adaptive modulation and coding mechanisms. In other words, a client with better signal strength gets better data rate and a client with poor signal strength gets poor data rate. Existing access points assume that client data rates are independent of the signal strength and the data rate is achievable if the client is located within some specified range of the access point.
Further, existing access points have limited radio and the fact that the spectrum is diverse necessities multiple radio in order to serve multiple clients. Some work has been done on implementing multiple radio based solutions for channel allocation however; none of the existing mechanisms work on spectrum allocation explicitly for multi radio based architecture. In addition, the single radio based solutions in existing access points are not extensible to a multi radio solution.
Also, existing mechanisms do not take into consideration the QoS requirements for different services. Thus, the access point does not serve users based on their QoS requirements.
In addition, some of the existing solutions provide for spectrum planning in enterprise wireless LAN. However, these solutions employ a central controller to know the interference maps of the access points in the enterprise setting; they also need to determine the number of clients associated with each access point. In case of an uncoordinated deployment such information would not be available. Due to the aforementioned drawbacks existing access points are not effective in serving the clients and utilizing the bandwidth effectively.